Fabric softening compositions, in particular fabric softening compositions to be used in the rinse cycle of laundry washing processes, are well-known to the consumer to provide fabrics with a soft and agreeable feeling. Such compositions are provided in two forms: concentrated compositions comprising more than 10% by weight of fabric softening agents and diluted compositions comprising less than 10% by weight of fabric softening agents.
Nevertheless, consumer acceptance of such compositions is determined not only by the performance achieved with these products but also by the aesthetics associated therewith. Viscosity of the product is therefore an important aspect of the successful formulation of such commercial products; stable medium to medium-high viscosities being highly preferred by consumer. By medium-high viscosities, it is meant viscosities of 50 cps to 150 cps when the fabric softening composition is in a diluted form and viscosities of 30 cps to 90 cps when the fabric softening composition is in a concentrated form.
However, a problem encountered with diluted compositions is that, contrary to concentrated compositions which exhibit a "self-building viscosity" due to their high amount of active, diluted compositions show a phase instability as well as a viscosity problem. Such a problem can be encountered either with an already-made diluted product or with a concentrated product as it is diluted.
To this end, thickeners such as compounds of the polyacrylamide, polysacharide or polyurethanes type have been widely used in such compositions. Disclosure of such compounds may be found in EP 0,422,179 and EP 0,309,052. However, a problem encountered with such thickeners is the necessity for them to be present at high levels to provide effective thickening effect. Whilst the use of such high levels would provide a good remedy to the problem, this would increase the formulation cost.
Compounds of the associative polymeric type or cross-linked cationic polymeric type are effective as thickeners, even at low levels. Disclosure of such compounds may be found in EP 0,385,789 and EP 0,422,179. However, the use of such compounds has been found to be detrimental to the phase stability and viscosity performance of the product upon storage and thus to the fabric softening performance of the product.
Not to be bound by theory, it is believed that such compounds are provided with anionic charges which destabilise the formulation equilibrium.
The potential for such a problem is enhanced when the softening composition comprises electrolytes.
The Applicant has now found that the addition of a component capable of sequestering metal ions, preferably in specific amounts, overcomes the problem.
By thickener is meant a component which has thickening properties, that is a compound which, when incorporated in a fabric softening composition, produces compositions with a higher viscosity in the presence of the polymer than in the absence of the polymer. Not included within the scope of this term are components having soil release properties such as those defined in U.S. Pat. No. 4,702,857.
It is therefore an advantage of the invention to provide compositions with good phase stability and viscosity.
It is another advantage of the invention to provide softening compositions with an effective softness performance.
It is a further advantage of the invention to provide softening compositions which allow the use of electrolytes without being detrimental to the formulation equilibrate.